RE46C180 datasheet(13/58 Pages) MICROCHIP

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DS20002275C-page 13

RE46C180

3.8

End-of-Life (EOL) Indicator

The EOL indicator is a user-programmable function. If

the EOL indicator function is enabled, then approxi-

mately every 15 days of continuous operation, TEOL,

the circuit will read an age count stored in EEPROM,

and will increment this age. After 10 years of operation,

an audible indication will be given to signal that the unit

should be replaced. The EOL indicator is the same as

the chamber test failure warning.

3.9

Tone Pattern

The smoke alarm tone pattern can be either a temporal

pattern, or a continuous pattern, depending on the

user’s selection. The temporal horn pattern supports

the NFPA 72® National Fire Alarm and Signaling

Code® for emergency evacuation signals. The

continuous pattern is a 70% duty cycle continuous

pattern.

If a CO alarm is detected through the IO, the unit will

sound the CO tone pattern. The CO tone pattern con-

sists of 4 horn beeps in every 5.8s. Each horn beep is

100ms long and separated by 100ms.

3.10 Horn Synchronization

The horn synchronization function is programmable by

the user.

In an interconnected system, if one unit goes into Local

Alarm, other units will also go into Remote Alarm. The

IO line is driven high by the origination local smoke unit,

and stays high during the alarm.

If the Horn Synchronization function is enabled, at the

end of every temporal horn pattern and when the horn

is off, the origination unit will drive IO low, then high

again. This periodic IO pulsing high and low will cause

the remote smoke units to go into and out of the

Remote Alarm repeatedly. Each time a unit goes into a

Remote Alarm, its timing is reset. The horn sound of all

remote smoke units will be synchronized with the horn

sound of the origination unit.

A protection circuit ensures that the unit which goes

into Local Alarm first will be the controlling unit that con-

trols the horn synchronization. The units that go later

into Local Alarm will not drive the IO line. This prevents

bus contention problem.

This function works with the temporal tone pattern only.

3.11 Auto Alarm Locate

Auto Alarm Locate (AAL) is also a user-programmable

function. To use AAL, the horn synchronization has to

be selected first. The purpose of AAL is to let users

quickly find the local alarm units just by listening. The

local alarm units will sound the temporal pattern without

interruption. The remote alarm units will sound the pat-

tern with interruption. Every four temporal patterns

(or 16s), the remote units are kept silenced for one pat-

tern (or 4s).

The originating unit conducts the IO cycling. Every four

temporal patterns the IO is driven low for one temporal

pattern. In the remaining three temporal patterns, the

IO is still pulsing to keep the horn synchronized.

The RLED of the origination unit and other local smoke

units will be turned on 10 ms every 1s. The RLED of the

remote smoke units will be off.

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